I don't think the ocean is equally saline everywhere: https://salinity.oceansciences.org/maps-global.htm

On average it's pretty close, but you can definitely get impacts from increased local salinity: https://onlinelibrary.wiley.com/doi/full/10.1111/gcb.16859 (just random ecamples)

https://www.scientificamerican.com/article/slaking-the-world... (view in incognito)